A cascade impactor is a serial connection of nozzle plates. The nozzle diameter, which is reduced from stage to stage, usually causes the gas velocity to increase. Between the individual nozzle plates, there are baffles covered with filter disks. A gas flow loaded with solids (particles) or liquids impinges on the filter and is deflected there. While fine loads follow the flow for low gas velocities, larger particles or droplets are deposited on the filter. The increasing gas velocity from cascade to cascade thereby separates the individual grain or liquid fractions. Cascade impactors may also be employed immediately in hot and chemically aggressive gases.
EP 2 378 090 A1 relates to an oil mist separator (1) for a crankcase ventilation means. It includes a first separator unit (2), which has at least one filter body (10) which is arranged in a blow-by gas path (11) in such a manner that blow-by gas can pass through it. A second separator unit (3) is provided, which is connected in parallel to said first separator unit (2) and arranged in a bypass path (18) that bypasses the first separator unit (2). Using a bypass valve (4), the bypass path (18) can be opened as soon as a differential pressure at the first separator unit (2) exceeds a predefined value.
The gas flows through two or more impactor stages arranged behind each other. The impactor as a separator and also an impactor cascade consisting of several stages are known. However, these individual stages are not variable. This means that the bore diameters and plate distances have a fixed design.